1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same and, more particularly, to a semiconductor device for use in a memory cell capacitor.
2. Description of the Related Art
A conventional cell capacitor is shown in FIG. 1. After a P-type silicon substrate 1 is thermally oxidized to form a field oxide film 2 having a thickness of 5000 .ANG., an oxide film 3 having a thickness of 100 .ANG. is formed. Ions As.sup.+ are then implanted to form an N.sup.+ layer 4. A polysilicon 5 is deposited and patterned to serve as a plate electrode.
The cell capacitor having a plane structure as shown in FIG. 1 is simple to manufacture and has been widely applied to the extent of 1 M-bit dynamic random access memory (DRAM). Since the plane structure, however, reduces the area of a cell when the degree of integration of the cell is enhanced, the thickness of a gate oxide film (oxide film 3) needs to be thinned to retain stored charges to some extent, which degrades the reliability of the oxide film 3. The plane structure cannot be physically applied to a cell capacitor of a DRAM of 4 M-bit or more.